The present invention relates generally to tire changing tools for engaging a tire and/or a wheel rim during a tire changing or tire servicing operation. More particularly, the present invention pertains to a mount/demount tool head for attachment to a shaft on a tire changing machine.
Tires generally include a resilient tire bead that must be forced over the outer perimeter of a wheel rim to remove the tire from the wheel rim or to install the tire onto the wheel rim. In many applications, the tire bead and the tire sidewall may be relatively stiff or rigid, creating difficulties in manually forcing the bead over the wheel rim. To overcome this difficulty, conventional tire changing tools are known in the art for installing a tire on a wheel rim or removing a tire from a wheel rim. Such conventional tools may include a pry bar, or a tire lever, that can be wedged between the wheel rim and the tire bead. However, conventional pry bar and tire lever devices can cause damage to the tire or the wheel rim. This type of damage is particularly harmful to modern low-profile wheel rims and those wheel rims having a cosmetic surface such as polished, chrome, or anodized rims.
Modern wheel servicing machines such as tire changers often include a base having a rotatable wheel mount for securely holding a wheel rim during tire changing operations. Such machines typically also include a swing arm having a vertically, or longitudinally, adjustable tire changing tool head, or mount/demount head, extending downwardly from the swing arm via a shaft for assisting in tire mounting and demounting. The mount/demount head is generally positioned near the wheel rim during tire mounting and demounting operations. Conventional mount/demount heads include a bead lifter portion that protrudes from the mount/demount head in a first direction substantially tangential to the outer perimeter of a wheel rim to be serviced. During tire removal, a tire bead may be lifted over the bead lifter, and the wheel may be rotated on the rotatable mount to separate the bead upwardly away from the bead seating flange on the wheel rim. Conventional mount/demount heads also typically include a tongue tool, or blade, extending from the mount/demount head in a tangential direction opposite the bead lifter. The tongue tool may have a substantially flat or slightly curved surface oriented in a plane generally parallel to the plane of rotation of the wheel rim when mounted on the wheel mount. The tongue tool provides a bearing surface across which a tire bead slides as the tire is installed over the bead engagement flange on the outer perimeter of the wheel rim. In conventional mount/demount heads, the bead lifter and the tongue tool are typically both integrally formed on one solid mount/demount head body.
In some applications, it may be possible for the tongue tool portion of the mount/demount head to contact the wheel rim, either intentionally or inadvertently during tire installation or tire removal. Such contact can cause damage to the wheel rim, especially when the mount/dismount head is made of a hard material such as a metal. To prevent such damage, some conventional mount/demount heads are made entirely of a non-metal material such as a plastic or a polymer material. The non-metal material may contact the wheel rim without causing excessive damage to the wheel rim.
In practice, operators of tire changing machines frequently encounter situations where it may be necessary to change the mount/demount head from a metal model to a non-metal model. The changing procedure is cumbersome and time-consuming because it generally requires manual removal of the existing tool and manual attachment of the replacement tool. Additionally, in many situations, the non-metal tool may not provide enough rigidity for subsequent operations, and the operator may be required to remove the non-metal tool and re-attach the metal tool. In a tire shop where numerous wheels may be serviced, it may be necessary to change the mount/dismount head several times during the course of a day, resulting in machine down time, reduction in operating efficiency and machine throughput, and operator fatigue.
To overcome the problems associated with frequently changing mount/demount heads during tire changing machine operation, others have developed quick-release and quick-attachment couplings to allow faster interchange between metal and non-metal mount/dismount heads. For example, U.S. Pat. No. 5,941,294 discloses a rim holding tire changer with a mount/dismount head connect structure. Additionally, U.S. Pat. No. 5,752,555 teaches a rim clamp tire changer mounting head adjustment release mechanism. However, such conventional couplings do not eliminate the need to manually change tool heads, they merely make the change-out process more efficient.
Still others have attempted to solve this problem by providing non-metal wear pads that attach to the surfaces on conventional metal mount/dismount heads that face the wheel rim. The wear pads provide some protection against wheel damage. However, the pads may become worn or damaged, requiring replacement. Additionally, if such pads are not monitored and replaced when necessary, inadvertent wheel rim damage may occur.
Another problem associated with conventional mount/dismount heads is that they are generally shaped to accommodate a specific wheel diameter or range of wheel diameters. Thus, when a tire changing machine operator services a large diameter wheel followed by a small diameter wheel, or vice versa, it is often necessary to change the mount/dismount head to accommodate the different wheel rim size.
What is needed, then, are improvements in mount/dismount tool heads for use with tire changing machines.